Bacterial vaginosis during pregnancy is associated with higher risks of pregnancy complications, including preterm birth, whether or not symptoms are reported. Bacterial vaginosis is currently considered to be a microbial imbalance of the lower genital tract characterized by low levels of “healthy” Lactobacillus and overgrowth of a mixed population of other bacterial genera, including Gardnerella, Atopobium, Prevotella, Mobiluncus, Sneathia, and other taxa. Many of these microbes are also common isolates from sites of intrauterine infection, including the placenta and amniotic fluid. These findings have motivated investigators to conduct clinical trials to examine the potential benefits and harms associated with screening and treatment of asymptomatic bacterial vaginosis in pregnant women, either applied to a general obstetric population or targeting women at increased risk for preterm delivery, such as those with prior preterm birth. This is particularly important in light of growing concerns about the effects of antibiotic use on long-term maternal and child health because of effects on their microbiomes.